The TRIM family of proteins mediates a number of recently reported antiviral activities mediated against diverse viruses. The best studied of these activities is the ability of the TRIM51 protein to inhibit the replication of certain retroviruses, including HIV-1, by binding determinants present on the viral capsid core during early stages of infection. Recent data suggests that other TRIM family proteins can affect HIV-1 replication at other steps in the viral replication cycle. Numerous studies suggest that TRIM family proteins can also negatively regulate the replication of a diverse range of viruses, including adenoviruses, herpesviruses and influenza viruses, although these activities remain poorly characterized. The recent finding that the expression of many TRIM family proteins are upregulated in response to interferon treatment also indicates that the TRIM family proteins represent an intracellular element of the innate immune system, acting to inhibit the replication of intracellular pathogens. Because of the tendency of TRIM51 to multimerize into high-order structures in cells, biochemical analysis of this protein has been unusually difficult. This will likely be true of other TRIM family members. My previous studies have utilized quantitative fluorescent microscopy to visualize and quantify the interactions occurring between TRIM51 and HIV-1 viral complexes in the cytoplasm. This project would develop retroviral vectors that induce the expression of epitope tagged TRIM family members and use these vectors to generate cell lines stably expressing these proteins. These vectors and cell lines will be useful in identifying TRIM proteins with antiviral activity against diverse viruses and expose novel interactions occurring in cells between viruses and TRIM family proteins. Once identified, these same vectors and cell lines will allow for the visualization of interactions occurring between TRIM proteins and viral proteins and/or genetic elements affected by TRIM activity. This will catalyze new areas of research for my lab and increase our understanding of the antiviral activity of TRIM family proteins.